Each piece was slowly rotated by 180° as a thin beam of high-energy X-rays – a trillion times stronger than X-rays used by hospitals – scanned its cells from different angles. Around 1,200 of these flat images were combined to create 3D maps of the fruit with a resolution of 7 microns – the size of a virus.

The resulting animations (see video, top right) of an apple and a pear reveal elaborate catacombs of empty space squeezed between the cells of the fruit.

Early rot

For years, scientists have thought that these voids must exist, carrying oxygen and carbon dioxide to and from the cells deep in the core of the fruit. However, this is the first time anyone has actually seen these microscopic channels.

The channels maintain their shape for up to six days after picking, as the fruit ripens and softens on the outside.

These structures may explain why, under identical storage conditions, pears tend to go brown while apples remain fresh for much longer, says Verboven.

Though the tunnels inside of pears have more interconnections, those inside apples have almost five times more volume, allowing for more gas transport.

Verboven hopes that this research can help the agriculture community save money by tailoring storage conditions to the architecture of fruit – species like pears with tiny “lungs” may need more oxygen not to rot.